This invention relates to zig-zag sewing machines in which control of the lateral jogging movements of a needle, of the neutral position of needle vibration, and the direction and magnitude of work feed may be accomplished by pattern cam means. It is known in the prior art to apply a clutch to one or a group of cams in a pattern cam controlled sewing machine. U.S. Pat. No. 2,983,240, May 9, 1961, by W. Engel, discloses a sewing machine in which a cam unit for influencing the needle position and the work feed control may be intermittently driven so as to provide for the sewing of closed stitch groups such as buttonholes. The buttonhole cam unit of the Engel patent is shifted lengthwise of the cam shaft when it is clutched to or disengaged therefrom. U.S. Pat. No. 3,585,876, June 22, 1971, by Marsh et al, eliminates the need for axially shifting the buttonhole unit of the Engel device for clutching the same. However, the Marsh device requires a traveling pawl arrangement which is extremely critical to make.